Objective lens-driving unit

Abstract

An objective lens-driving unit comprising a lens supporting means for supporting the objective lens having an optical axis vertical to a recording medium on which light beams converge through the objective lens so as to attain optical recording, optical playing and optical erasing of information on the recording medium; at least one driving means for driving said lens supporting means in the tracking direction; a driving means for driving said intermediate supporting means in the focusing direction, wherein said tracking direction-driving means comprises a magnetic circuit that produces magnetic flux in the circumferential direction of the recording medium, and a tracking direction-driving coil that is positioned to cross a gap formed in the magnetic circuit to thereby receive an electro-magnetic force due to an interaction between the magnetic field of the magnetic circuit and the current passing through said coil, said tracking direction-driving coil being positioned within the excitation area of the magnetic circuit even when said coil moves in the focusing direction.

What is claimed is: 
     
       1. An objective lens-driving unit comprising a lens supporting means for supporting the objective lens having an optical axis vertical to a recording medium on which light beams converge through the objective lens so as to attain optical recording, optical playing and optical erasing of information on the recording medium; an intermediate supporting means for supporting said lens supporting means by use of springs that are movable in the tracking direction; a fixed supporting means for supporting said intermediate supporting means by use of springs that are movable in the focusing direction; at least one driving means for driving said lens supporting means in the tracking direction, said tracking direction-driving means being positioned between said fixed supporting means and said lens supporting means; a driving means for driving said intermediate supporting means in the focusing direction, said focusing direction driving means being positioned between said fixed supporting means and intermediate supporting means, wherein said tracking direction-driving means comprises a magnetic circuit that produces magnetic flux in the circumferential direction of the recording medium, and a tracking direction-driving coil that is positioned to cross a gap formed in the magnetic circuit to thereby receive an electro-magnetic force due to an interaction between the magnetic field of the magnetic circuit and the current passing through said coil, said tracking direction-driving coil being positioned within the excitation area of the magnetic circuit even when said coil moves in the focusing direction.   
     
     
       2. An objective lens-driving unit according to claim 1, wherein said focusing direction driving means comprises a magnetic circuit with a gap and a focusing direction-driving coil positioned to cross said gap to thereby receive an electro-magnetic force in the focusing direction due to an interaction between the magnetic field of the magnetic circuit and the current passing through said coil. 
     
     
       3. An objective lens-driving unit according to claim 2, wherein a velocity-detecting coil is laid upon said tracking direction-driving coil and/or said focusing direction-driving coil, thereby attaining the detection of the velocity of the driving of the tracking direction-driving coil and/or the focusing direction-driving coil. 
     
     
       4. An objective lens-driving unit according to claim 1, wherein a velocity-detecting coil is laid upon said tracking direction-driving coil and/or said focusing direction-driving coil, thereby attaining the detection of the velocity of the driving of the tracking direction-driving coil and/or the focusing direction-driving coil. 
     
     
       5. An objective lens-driving unit according to claim 1, wherein at least one flexible printed circuit is disposed on said fixed supporting means in such a manner that one end of the flexible printed circuit is exposed to the outside of the fixed supporting means, lead wires led from at least one selected from said tracking direction-driving coil and said focusing direction-driving coil being connected to said flexible printed circuit and wires through which current is supplied to said coil being connected to said exposed portion. 
     
     
       6. An objective lens-driving unit according to claim 1, wherein the portion(s) of at least one selected from said lens supporting means, said intermediate supporting means and said fixed supporting means, to which one end or both ends of each of said springs is fixed, is separable into two parts. 
     
     
       7. An objective lens-driving unit according to claim 6, wherein at least one end of each of said springs are fixed to at least one of said supporting means by an adhesive in a manner to be positioned between the two parts.